title: MAGUKs, scaffolding proteins at cell junctions, are substrates of different proteases during apoptosis.
abstract: A major feature of apoptotic cell death is gross structural changes, one of which is the loss of cell-cell contacts. The caspases, executioners of apoptosis, were shown to cleave several proteins involved in the formation of cell junctions. The membrane-associated guanylate kinases (MAGUKs), which are typically associated with cell junctions, have a major role in the organization of protein-protein complexes at plasma membranes and are therefore potentially important caspase targets during apoptosis. We report here that MAGUKs are cleaved and/or degraded by executioner caspases, granzyme B and several cysteine cathepsins in vitro. When apoptosis was induced by UV-irradiation and staurosporine in different epithelial cell lines, caspases were found to efficiently cleave MAGUKs in these cell models, as the cleavages could be prevented by a pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp(OMe)fluoromethylketone. Using a selective lysosomal disrupting agent L-leucyl-L-leucine methyl ester, which induces apoptosis through the lysosomal pathway, it was further shown that MAGUKs are also cleaved by the cathepsins in HaCaT and CaCo-2 cells. Immunohistological data showed rapid loss of MAGUKs at the sites of cell-cell contacts, preceding actual cell detachment, suggesting that cleavage of MAGUKs is an important step in fast and efficient cell detachment.
authors.affiliation: Department of Biochemistry and Molecular Biology, J Stefan Institute, Ljubljana, Slovenia.
authors.forename: S
authors.initials: S
authors.lastname: Ivanova
authors.forename: U
authors.initials: U
authors.lastname: Gregorc
authors.forename: N
authors.initials: N
authors.lastname: Vidergar
authors.forename: R
authors.initials: R
authors.lastname: Javier
authors.forename: D S
authors.initials: DS
authors.lastname: Bredt
authors.forename: P
authors.initials: P
authors.lastname: Vandenabeele
authors.forename: J
authors.initials: J
authors.lastname: Pardo
authors.forename: M M
authors.initials: MM
authors.lastname: Simon
authors.forename: V
authors.initials: V
authors.lastname: Turk
authors.forename: L
authors.initials: L
authors.lastname: Banks
authors.forename: B
authors.initials: B
authors.lastname: Turk
mesh_terms: D017209:Apoptosis; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D002477:Cells / Q000166:cytology / Q000201:enzymology*; D051528:Guanylate Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007365:Intercellular Junctions / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D045170:Matrix Attachment Regions; D010447:Peptide Hydrolases / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D051528:Guanylate Kinases; D010447:Peptide Hydrolases